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Help please, question about possibilities.... — Parallax Forums

Help please, question about possibilities....

RhinoRhino Posts: 5
edited 2005-05-17 15:36 in BASIC Stamp
I am planning on making blinkers for my car out of about 18 LED's EACH (so I will need to individually control 36 LED'S).··idea.gif· was wondering how in the world I could do this and which parallax product or kit would be best suited for this project, I am a complete newbie, I did some pascal programming in high school, but I am sure I will need a little help.· I need the LED's to come on in a sequence (order) and stay on until the last LED is lit and then come on again in the same sequence when the blinker is turned on.· The LED's are coming with 12V resistors for each LED.· Which of·the parallax·products would get the job done the best?· I also would like to have an option of having all LED's on at the switch of a button or have different patterns that they can do, but the 1st main priority is to get them hooked up in sequence with the blinkers.· Thanks in advance.
···· In Christ,
··········· Ryan roll.gif

Comments

  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-05-09 17:03
    Being an admitted noobie, you should start at the beginning with our "What's A Microcontroller?" text. Once you've got that down it won't take much to get your project going -- until then, anything we offer will likely be over your head and more confusing than useful.

    You can do what you want with a BS2, a few 74HC595 shift-registers, ULN2803 Darlington arrays to match each '595, and a tiny bit of code -- but read WAM first. You can download WAM from our web site.

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    Jon Williams
    Applications Engineer, Parallax
    Dallas, TX· USA
  • dandreaedandreae Posts: 1,375
    edited 2005-05-09 17:46
    We also offer a MAX7219 LED driver that can control up 64 discreet LEDs.· Here is a link for more information:·

    http://www.parallax.com/detail.asp?product_id=603-00001

    Dave

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    Dave Andreae

    Tech Support
    dandreae@parallax.com
    www.parallax.com

    ·
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-05-09 17:50
    Yep, forgot all about that -- but it's easy to forget when it has a $11 price (Digi-Key) versus about a buck for a 74HC595/ULN2803 pair.

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    Jon Williams
    Applications Engineer, Parallax
    Dallas, TX· USA
  • RhinoRhino Posts: 5
    edited 2005-05-10 05:32
    So would buying that "what is a microcontroller" thing from radio shack be the best bet?
    I need to hook this thing up to my car's battery for the power (12V),
    and get a signal from the blinker to tell it when to turn the LED's on,
    and I guess have a switch mounted inside to turn on/off different features,
    and which board will support that many individual LED's (36),
    and also would changing the volts from my cars 12v to whatever the microcontroller needs mean that I no longer need to use a resistor per each LED?
    I just want to make one purchase and know that I can make it work with what I got and not get frustrated trying to do something that I need to buy something else to·do.
    Thanks again. And I will read that article ASAP I have already started on it.
    In Christ,
    Ryan

    Post Edited (Rhino) : 5/10/2005 5:36:44 AM GMT
  • allanlane5allanlane5 Posts: 3,815
    edited 2005-05-10 13:57
    1. You MUST use a resistor to limit the current through each LED. An LED is a 'current' device -- which means there's nothing in there to limit the current. Too much current, and the LED acts like a fuse. Thus the resistor to limit the current to around 15 mA per LED.

    2. The BS2 will work off of a 12-volt car battery. You may need an additional capacitor on the Vin to Vss line, to filter some of the noise from the alternator. A car's 12-volt line is very noisy.
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-05-10 14:37
    If using a multiplexer like the MAX7219, the current through all LEDs is controlled with a single control resistor, plus the brightness setting of the device. I think it would be simpler to use 74HC595s combined with ULN2803s, and in that case, current limiters would be required for each LED.

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    Jon Williams
    Applications Engineer, Parallax
    Dallas, TX· USA
  • Ryan ClarkeRyan Clarke Posts: 738
    edited 2005-05-10 15:41
    Speaking of car power, aren't there some pretty nasty spikes on the lines when you turn on the ignition?

    Ryan
  • RhinoRhino Posts: 5
    edited 2005-05-12 06:18
    After reading a few chapters I see that I will need at least 36 I/O pins to seperately control each LED is this correct?
  • KenMKenM Posts: 657
    edited 2005-05-12 06:50
    Rhino, yes and no.

    If these LEDs are simply going to replace the existing bulbs, do you need to control then with a stamp? If the function will be exactly the same as the current setup, then there is no need to use a micro controller, and simply replace the bulbs with "groups" of LEDs.

    Assuming you are using "standard 2 volt 15 mA" LEDs, my suggestion would be to wire 4 LEDs in series and one current limiting resistor per group of four.

    For brake lights, tail-lights and such, auto manufacturers do not run a single LED and resistor. They will run LEDs in series with one resistor per group of LEDs.

    You will experience some variance in brightness however as the vehicle voltage will typically range from 12 to 15 volts.

    The switch in the schematic is your blinker relay, brake light switch or module.
    Rhino said...
    After reading a few chapters I see that I will need at least 36 I/O pins to seperately control each LED is this correct?
    carled.jpg
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  • allanlane5allanlane5 Posts: 3,815
    edited 2005-05-12 12:49
    My understanding was he wanted to control these LED's in 'patterns', so he could have a string of LED's with a 'ripple' of light. Otherwise, Ken is quite correct, you CAN control groups of LED's as he said.
  • RhinoRhino Posts: 5
    edited 2005-05-13 06:26
    Correct I have a few different patterns that all involve specific timing for EACH LED to be on and off at specific times when the blinker relay is on and then also when certain other switches are activated, so I would need I/O's for each LED and each "switch" or relay input correct?
  • KenMKenM Posts: 657
    edited 2005-05-13 14:45
    Rhino,

    If more than one LED will have the EXACT pattern then "those" LEDs can be connected in series.



    If every single of your 36 LEDs will do something different the each LED will be wired with its own current limiting resitor.

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  • RhinoRhino Posts: 5
    edited 2005-05-17 06:53
    Ok, so no two LED's would have the exact same pattern, so......


    ?????Which board will support at least 36 individual LED's doing something totally different at different times from each other, basically I believe I need at least 36 I/O but I couldn't find a stat like that on any of the boards listed????? Thanks
  • ForrestForrest Posts: 1,341
    edited 2005-05-17 13:40
    See Stampworks experiments 23 and 23B available here www.parallax.com/html_pages/downloads/sw/sw.asp

    These show you how to control up to 16 LED's with just 3 Stamp pins. Each group of 8 LED's is controlled with a 74HC595 shift register and 9 resistors.
  • Jon WilliamsJon Williams Posts: 6,491
    edited 2005-05-17 15:36
    If you're looking at controlling 36 individual LEDs I would suggest a multiplexer like the MAX7219 or the MC14489.

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    Jon Williams
    Applications Engineer, Parallax
    Dallas, TX· USA
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